arm64: Add per-cpu infrastructure to call ARCH_WORKAROUND_2

In a heterogeneous system, we can end up with both affected and
unaffected CPUs. Let's check their status before calling into the
firmware.

Reviewed-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index c1eda6be77588240a001bbfdda67908ff56af58b..cd91ca0250f1c0f51e21dc4ff1c15044d98af30b 100644 (file)
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -233,6 +233,8 @@ enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
 #endif /* CONFIG_HARDEN_BRANCH_PREDICTOR */
 
 #ifdef CONFIG_ARM64_SSBD
+DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
+
 void __init arm64_update_smccc_conduit(struct alt_instr *alt,
                                       __le32 *origptr, __le32 *updptr,
                                       int nr_inst)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f33e6aed3037ce295af2da804749664909eb3d1f..29ad672a6abdf52549bf80257394245366781abd 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -140,8 +140,10 @@ alternative_else_nop_endif
 
        // This macro corrupts x0-x3. It is the caller's duty
        // to save/restore them if required.
-       .macro  apply_ssbd, state
+       .macro  apply_ssbd, state, targ, tmp1, tmp2
 #ifdef CONFIG_ARM64_SSBD
+       ldr_this_cpu    \tmp2, arm64_ssbd_callback_required, \tmp1
+       cbz     \tmp2, \targ
        mov     w0, #ARM_SMCCC_ARCH_WORKAROUND_2
        mov     w1, #\state
 alternative_cb arm64_update_smccc_conduit
@@ -176,12 +178,13 @@ alternative_cb_end
        ldr     x19, [tsk, #TSK_TI_FLAGS]       // since we can unmask debug
        disable_step_tsk x19, x20               // exceptions when scheduling.
 
-       apply_ssbd 1
+       apply_ssbd 1, 1f, x22, x23
 
 #ifdef CONFIG_ARM64_SSBD
        ldp     x0, x1, [sp, #16 * 0]
        ldp     x2, x3, [sp, #16 * 1]
 #endif
+1:
 
        mov     x29, xzr                        // fp pointed to user-space
        .else
@@ -323,8 +326,8 @@ alternative_if ARM64_WORKAROUND_845719
 alternative_else_nop_endif
 #endif
 3:
-       apply_ssbd 0
-
+       apply_ssbd 0, 5f, x0, x1
+5:
        .endif
 
        msr     elr_el1, x21                    // set up the return data